Moving of Magnetic Clusters Driven by an Applied Eccentric Rotational Magnetic Field

Author

Hsu, Chien

Date

2016-04-22

Advisor

Biswal, Sibani Lisa

Degree

Master of Science

Abstract

Magnetic swimmers have been studied with the purpose of applying them to mimic the motion of organisms in fluids. Clusters formed by self-assembled magnetic particles is one the possible approaches for that purpose. A considerable amount of effort has been made on applying uniaxial, biaxial, and triaxial magnetic fields to study self-assembled clusters. For the case where biaxial magnetic fields are applied, a circular rotational magnetic (CRM) field is usually adopted. Relevant results concerning the behavior of these clusters in eccentric rotational magnetic (ERM) fields are limited. This may be due to the limited number of stable conformations formed in such a magnetic field is linear. In this thesis, we show that several unique metastable cluster structures can form in an ERM field. The clusters are formed by applying a CRM field to a dispersion containing paramagnetic particles to form a specific configuration and then the magnetic field is switched to an ERM those field to visualize new dynamics. These 2-D clusters can be driven by the applied magnetic field, yielding an appreciable net displacement, and exhibit specific dynamic behavior. The behavior of these clusters is influenced by the surface charge of the comprising magnetic particles, the strength and the frequency of the applied magnetic field, and the viscosity of the dispersion fluid. A model is proposed to simulate the phenomena observed in the experiment which describes successfully the displacement of a pentamer colloidal cluster.